Conventionally, the weather strip is used to fill the gaps between a body panel and a bonnet panel or a door panel of an automobile, and is mounted on the body panel by using a fastener made of synthetic resin such as the one illustrated in FIG. 3.
Referring to FIG. 3 showing a conventional fastener of the type disclosed in U.S. Pat. No. 3,494,244 issued to Wayland on Feb. 10, 1970, to the end of retaining a weather strip 2 which serves as a first member in this case, a fastener 21 is provided with an umbrella shaped cap 3 which retains the weather strip 2 by being received therein via an engagement hole 2a provided in the weather strip 2, and a stem portion 22 which is to be passed through a through hole 4a provided in a body panel 4 of an automobile serving as a second member on which the weather strip 2 is to be mounted. The stem portion 22 has a diameter slightly smaller than the diameter of the through hole 4a, and is provided with three annular flanges 23a through 23c in mutually spaced relationship in the longitudinal direction. The outer diameter of these flanges 23a through 23c is slightly larger than the diameter of the through hole 4a. Therefore, when pushing the stem portion 22 into the through hole 4a, the axial force therefor causes the flanges 23b and 23c to be elastically contracted thereby allowing them to be passed through the through hole 4a to the other side of the steel panel 4 where the flange 23b restores its original condition and secures the fastener 21 to the steel panel 4.
In such a conventional fastener 21, when pushing the fastener 21 into the through hole 4a of the body panel 4, since the flanges 23b and 23c had to be compressed for insertion, a relatively large force was required for this process. Therefore, it was a problem that the work involved in the use of the fastener required more efforts than desired.